ub: cdma: finish the jfce and jfae release even if the context lock is busy · Pull Request !1135 · OpenCloudOS/OpenCloudOS-Kernel

## Problem

`cdma_delete_jfce()` and `cdma_delete_jfae()` are the `->release()` callbacks
of the CDMA event file descriptors. They take `cfile->ctx_mutex` with
`mutex_trylock()` and, when another user of the same `cfile` holds the lock,
return `-ENOLCK` without doing anything else.

`->release()` runs from task_work or the delayed-fput workqueue and its return
value is discarded by the VFS, so nothing retries the work:

- the jfce/jfae object and its device id stay allocated;
- the reference that `cdma_alloc_jfce()` / `cdma_alloc_jfae()` took on the
  cfile is never returned, which keeps `cdma_release_file()` from ever running.
  The whole `struct cdma_file` — its idr, its umap list and its registered mmu
  notifier — then leaks, one per racing close.

Reaching it only needs one thread of the process to be inside an
ioctl/mmap/close that holds `ctx_mutex` while another thread closes the event
fd.

## Fix

Take the mutex instead of trying it, so the release always completes. The
callback cannot deadlock on it: it is only reached through the deferred fput
paths, which run after the ioctl/mmap/close call that holds the lock has
returned to userspace, and the driver's own `cdma_close()` path already takes
the same mutex with `mutex_lock()` before running the equivalent context
cleanup.

## Verification

- `scripts/checkpatch.pl --no-signoff --strict`: 0 errors, 0 warnings.
- arm64 build (`CONFIG_UB=y`, `CONFIG_UB_UBUS`, `CONFIG_UB_UBUS_BUS`, `CONFIG_UB_UBUS_USI`, `CONFIG_UB_UMMU_CORE`, `CONFIG_UB_UBASE`, `CONFIG_UB_CDMA=y`, target `drivers/ub/cdma/`, Bootlin aarch64 gcc 15.3.0, `W=1`): baseline and patched trees both build with exit 0 and produce all 23 objects; both show the same single pre-existing `-Wunused-but-set-variable` warning in `cdma_jfc.c`, which is not touched here.
- Not run: runtime test. No UB/CDMA hardware is available in the development environment, so the racing close was not exercised.

类型	指派人员	状态
审查	zoucao Huang Cun Jianping Liu	已完成 (0/0人)
测试	Jianping Liu	已完成 (0/0人)

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